1. Field of the Invention:
The invention relates in general to elevator systems, and more specifically to new and improved car position indicators for elevator systems.
2. Description of the Prior Art:
Elevator systems conventionally provide a car position indicator in each elevator car, to indicate to the passengers the position of the elevator car relative to the floors, and a car position indicator may also be disposed external to the car at a selected floor, or floors, such as at the main floor. The car position displayed on the position indicator is normally the advanced floor position of the car, i.e., the actual floor position of a stationary car, and the closest floor to the car at which the elevator car can make a normal stop, for a moving car.
With an electromechanical floor selector, the car position indicator is driven by contacts actuated as the floor selector is driven in synchronism with the movement of the elevator car. U.S. Pat. No. 2,085,135 is an example of this type of position indicator. With a solid state floor selector, the advanced floor position may be developed by generating pulses responsive to car movement which are summed to provide a continuous car position, and this signal may be used to provide index pulses for an up-down counter which provides a car position signal related to a floor. U.S. Pat. No. 3,750,850 is an example of a floor selector which generates the advanced car position in this manner, and copending application Ser. No. 358,429, filed May 8, 1973, which is assigned to the same assignee as the present application, discloses a car position indicator which utilizes a signal such as provided by an up-down counter to energize a different lamp for each floor, in order to indicate car position.
Car position indicators which utilize a different incandescent lamp for each floor require a substantial amount of time to wire in the field, because the number of wires which must be connected to the car position indicator fixture is quite large, and the wiring is not standardized. In other words, each elevator installation may have a different number of wires, and the display fixture portion of the car position indicator may be a different size for each installation having a different number of floors. Also, the constant cycling of the incandescent lamps causes early failure thereof, which increases maintenance costs.
A rotatable disc with numbered slides disposed on its periphery, a single lamp, and a display screen for showing a slide image, has been used to reduce the number of wires and the number of incandescent lamps, but this type of car position indicator is limited to elevators which have a maximum speed of 300-350 feet per minute (90-100 meters per minute). With speeds faster than this, the display blinks on and off so rapidly that it is difficult to read. This type of display is also subject to mechanical problems, such as getting out of synchronism with the elevator car, focus problems, and early failure of the lamp due to the constant cycling thereof.
Separate fixed slides with separate low voltage lamps and associated display screens have been used for higher speed elevator cars, but the field wiring is not standardized, the lamp replacement is difficult, it requires a step-down transformer, and it is subject to focus and contrast problems. The relatively poor contrast usually dictates that instead of using a single car position display mounted over the door of the elevator car, two displays be used, one mounted on each side of the door above the main and auxiliary car call pushbutton stations.
Thus, it would be desirable to improve the car position indicator for elevator systems by reducing the number of wires which are required to be connected to the position indicator in the field, by standardizing the display fixture size and wiring thereof so the same external connections are made for each installation, regardless of the number of floors and the desired display notations for each floor, and by using display elements which have a long service life, notwithstanding on-off cycling.